Alkoxylated alkylamines and alkyl ether amines, particularly ethoxylated alkyl-amines and ethoxylated alkyl ether amines, have many applications in industry. They can be usefully employed as adjuvants in cleaning formulations, textile processing aids, dye transfer inhibitors, acid thickeners, detergent boosters, degreasers, anti-static agents, and the like.
Alkoxylated alkylamines and alkoxylated alkyl ether amines are materials possessing the following general structure (I):
wherein R is selected from a linear or branched, saturated or non-saturated alkyl group containing 8-22 carbon atoms or a group of the formula:R—O-(A)a-(B)b-(C)c,wherein A and B are alkylene oxide groups containing 2-4 carbon atoms, C is an alkylene group containing 3-4 carbon atoms, a, b each vary from 0-5, c is 1, X, Y, Z are alkylene oxide groups containing 2-4 carbon atoms, x is 1, and y varies from 1-15.
As illustrated by general formula (I), the alkoxylated alkylamines/alkoxylated alkyl ether amines possess a surfactant structure which is composed of the lipophilic groups (R) and the hydrophilic groups (polyalkylene oxide). In their designed applications, the performance of alkoxylated alkylamines and alkoxylated alkyl ether amines is dependent on a balance between the lipophilicity and the hydrophilicity provided by these groups.
Even when the lipophilicity-hydrophilicity balance does exist, the performance of the alkoxylated alkylamines/alkoxylated alkyl ether amines is not necessarily optimal. Traditionally, these materials are prepared from the base-catalyzed alkoxylation of the corresponding alkylamines/alkyl ether amines. Such an alkoxylation reaction is actually the polymerization reaction of alkylene oxide, including the characteristic propagation and chain transfer steps of the polymerization process. For this reason, the resulting alkoxylated alkylaminelalkyl ether amine is not a pure compound, but a mixture of many homologs.
As an example, FIG. 1 illustrates the homolog distribution of ethoxylated tallow amine prepared from the regular (hydroxide-catalyzed) ethoxylation of tallow amine with 5 moles of ethylene oxide. As shown in FIG. 1, the resulting ethoxylated product is not a single compound containing five (CH2CH2O) units as the general structure (structure I, with 2x+2y=5) may suggest. Instead, the product is a mixture of several homologs whose total of ethylene oxide units varies from 2 to 10. Among these homologs, only those in the middle of the distribution range (3EO-5EO) have the proper liphophilic-hydrophilic balance and, therefore, are preferred. Homologs with a shorter EO chain length (<3EO) or a longer EO chain length (>5EO) are not desirable, since they are either too lipophilic or too hydrophilic for the applications utilizing this product. Therefore, it is advantageous to develop an alkoxylation process that results in alkoxylated products with peaked distribution.
As covered in the prior art, an ethoxylation process offering peaked distribution has been developed; the ethoxylated alkylamines/alkyl ether amines having peaked distribution were successfully prepared by ethoxylation of the starting alkylamine catalyzed by a Lewis acid. However, hazardous property of the catalyst, lower reaction rate, degradation of the product colour, and formation of by-products have seriously limited the utilization and usefulness of this acid-catalyzed ethoxylation process and adversely affect the properties and the attractiveness of the ethoxylated products.
Accordingly, it is an object of the present invention to develop a process for the preparation of alkoxylated ethoxylated alkylamines and alkyl ether amines, particularly ethoxylated alkylamine and ethoxylated alkyl ether amine with peaked distribution having greatly minimized drawbacks compared to those associated with the acid-catalyzed process.